This application relates to an apparatus and method for removing noxious materials from contaminated emission gases containing the same. More particularly, this invention relates to an apparatus for either physical or chemical removal of noxious materials from contaminated emission gas streams wherein the contaminated gases are intimately admixed with a finely atomized liquid and the contaminants are transferred from the emission gases to the liquid.
The emission of air-borne contaminants from stack gases and other similar sources has become a major contributor to air pollution and the subject of rather stringent legislation by both federal and state agencies. Air-borne pollutants can exist in several forms. Some are considered to be "particulate matter" which is usually defined as any material emitted as liquid or solid particles or both, e.g. smoke, fly ash, fats, oils, greases, dust, saw dust, metal oxides and salts, and liquid hydrocarbons. Other contaminants are in gaseous forms such as sulfur oxides, mercaptans, sulfides nitrogen oxides, and organic compounds such as carbonyls and volatile hydrocarbons.
With the increase of industrial processes and the ever expanding world population, more and more noxious materials are being released to the atmosphere causing severe air contamination, particularly in heavily populated areas. To stem the tide of rising air pollution, it has become imperative that governmental controls be placed upon the amount of air pollutants which can be emitted into the surrounding environment. As technology becomes more and more proficient, the regulation of air-borne pollutants becomes more stringent.
Various methods and apparatus for the removal of particulate matter from stack gases and the like have been devised. These usually involve the precipitation, agglomeration or entrainment of the air laden particles and function with varying degrees of success. Typical of such air cleansing devices are those found in U.S. Pat. No. 1,062,446, issued May 20, 1913; U.S. Pat. No. 2,937,712, issued May 24, 1960; U.S. Pat. No. 3,248,858, issued May 3, 1966; U.S. Pat. No. 3,348,830, issued Oct. 24, 1967; U.S. Pat. No. 3,488,924, issued Jan. 13, 1970; and U.S. Pat. No. 3,581,463, issued June 1, 1971. These patents all describe devices for the scrubbing of contaminated air with streams of water and, in most cases, involve the use of spray nozzles, as a means of water/gas contact. U.S. Pat. Nos. 3,248,858 and 3,581,467 avoid the use of nozzles in bringing about contact of contaminated gases with a water mist by utilizing either fan means or a rotating cone. In U.S. Pat. No. 3,248,858, a water mist for contact with vaporized grease particles is generated by means of a rapidly rotating inverted truncated cone extending into a water reservoir which pulls the water up through the cone along its outside walls and sprays it outwardly over the top edge in the form of a mist.
In U.S. Pat. No. 3,581,467, water is vaporized by means of a fan which creates an upward, vertical movement of both gas and water vapor through a vertical, uniform diameter, cylindrical duct, which of necessity has a non-horizontal lower portion part of which must be submerged in a water reservoir.
These structures are typical of the prior art. One problem associated with most prior art devices is that they are not suitably equipped to efficiently bring about intimate mixing of contaminated gases with water or liquid particles when large volumes of gases are involved. Sprays from nozzles are directional in nature and may not be evenly distributed throughout the gas-liquid contact zone. Moreover, spray droplets may not be small enough in size to present sufficient surface area to adequately contact all gas contaminants. Nozzles also become plugged presenting time-consuming and costly maintenance problems. Devices such as disclosed in U.S. Pat. No. 3,581,467, are only partially open to the atmosphere for conducting gaseous materials up the duct since the lower portion of the duct must be submerged in a liquid reservoir. The positioning of the duct into the liquid reservoir not only may inhibit the flow of gases into the duct, but limits the lower duct configuration thereby preventing the optimum utilization of the liquid. For example, with the lower portion of the duct below the liquid surface, the vibration of the duct causes the size of the water droplets leaving the surface of the liquid reservoir to be larger than when the duct does not extend below the surface and may cause more liquid to be drawn up in vortical movement through the duct than is necessary. Moreover, larger droplet sizes reduces the liquid surface area and lowers the opportunity for gas-liquid contact.